This application proposes formation of a four-institution consortium, the Eastern Prevention Trials Unit (EPTU) consisting of Yale University School of Public Health (New Haven, CT), State University of New York/Downstate Medical Center (SUNY-DMC) (Brooklyn, NY), the Biomedical Center on AIDS/St. Petersburg State University (SPSU) (St. Petersburg, Russia) and the Center for AIDS Intervention Research (CAIR) at the Medical College of Wisconsin (MCW) (Milwaukee, WI). The investigators propose to enroll into HPTN protocols suitable individuals residing in Connecticut, Brooklyn and St. Petersburg, Russia. MCW will contribute expertise in community-based behavioral intervention studies to the EPTU, particularly in Russia. All four institutions have overlapping geographical and research interests in HIV prevention in the eastern US (ongoing joint studies) and Eastern Europe (AIDS International Training and Research Programs in Russia [Yale/MCW/SPSU] and Eastern Europe [SUNY-DMC]). The EPTU could contribute to the HPTN by: (1) identifying effective prevention strategies; and (2) facilitating their evaluation through the Unit's large international population capacity (population base of 6 million in Connecticut and Brooklyn and 6 million in St. Petersburg). Large segments of this population base have high HIV incidence rates driven by political, economic, social, and demographic instability. The application attributes four significant strengths to the proposed consortium. First, it could provide access to populations in which the HIV epidemic is still in its early phases (St. Petersburg) and in which the epidemic has matured (Brooklyn and Connecticut). Second, it has HIV prevention research management skills and on-site expertise needed to recruit and retain these populations in prevention intervention trials. Third, it has the national and international theoretical and practical scientific expertise to assist the HPTN in carrying out its extensive and complex mandate. Fourth, the EPTU has the capacity to expand to increase the number of high-risk or infected individuals for enrollment in larger prevention intervention studies. The Yale/MCW/SPSU St. Petersburg AITRPP has established linkage points with critical non-governmental organizations (NGOs) throughout Russia concerned about AIDS. The AITRP at SUNY-DMC has similar connections that can foster expansion to sites in Poland. Project SIDA in Kinshasa, Congo, is an additional possible collaborator that could be brought into the EPTU should HPTN supplemental funds become available at a later date.